Motor graders are common vehicles used in, among other things, road construction and maintenance for displacing, distributing, and leveling material such as soil, gravel, snow, and the like. Such machines typically include front and rear wheels with a relatively high main frame connecting the two. A work blade downwardly depends from the main frame. When in use the blade can be lowered so as to contact the ground below and when the vehicle moves forward, the material on the ground is pushed forward by the blade. The blade is also rotatable so as to displace more or less material as is desired for the given job.
With some motor graders, the rear of the vehicle is provided with tandem rear drives such that the overall machine has six wheels. Tandem rear drives provide the motor grader with additional power, traction and stability. Another feature common on motor graders is the attachment of a ripper tool on the rear of the vehicle. Such tools have a plurality of downwardly directed tines or claws which penetrate and drag along the ground when the vehicle moves forward. Ripper attachments are useful for breaking the top surface of the ground, be it compacted soil, turf, gravel or pavement. Once ripped, the ground can then be graded with the aforementioned blade.
While such machines are very useful and have been met with substantial commercial success since their introduction, improvements continue to be sought. For example, it would be advantageous to provide a motor grader with an adjustable center of gravity. One instance where this would be desirable would be when using the ripper attachment. As such a tool is placed behind the vehicle and creates a significant downward drag, it would be beneficial to have a vehicle with a center of gravity positionable to best address that load.
In addition, in certain operations it may be desirable to operate the grader with the blade rotated at an aggressive angle, i.e., up to being practically parallel with the longitudinal axis of the grader. However, with current technology this may inadvertently result in tire or wheel damage if the blade is rotated into engagement with the rear tandem wheel.
In still further instances, the motor grader might be tasked with grading the surface in question down to a tenth of an inch or less. For example, if finish grading a road surface just prior to application of concrete or asphalt, every deviation from that tolerance will result in additional concrete or asphalt being required, thereby increasing the cost of the job. With current graders, no ability exists to adjust the wheel base and thus if a surface to be graded is particularly uneven, this will result in a limited ability to meet that tolerance as the movement of one wheel due to an obstruction or the like on the surface to be graded will result in vertical displacement of the grader and blade. Alternatively, the grader will have to make multiple passes to meet the tolerance, also resulting in additional cost.
Finally, the main frame of a typical grader is able to turn or articulate with respect to the chassis or rear of the grader. As currently available graders have a wheel base of fixed length, the articulation angle and turning radius of the grader are also fixed. However, in certain situations it may be desirable to have an adjustable articulation angle. One example would be when grading a surface provided at an incline to the roadway such as a berm, culvert, ditch or the like. In such situations, the rear wheels of the grader may be on a flat level surface with the front wheel, main frame and blade articulated away from the rear wheels so as to be over the inclined surface being graded.